rssi error

Dear all

I am working on the active RFID.
Reader will have the whip antenna at the fixed location where as the TAG will have the inverter F antenna.
My issue is when TAG and the reader is placed at fixed distance and when TAG is rotated at different orientation i will see the large variation/deviation in the RSSI value, how to minimize this error with different orientation?

Or is it possible to get ominidirectional radiation pattern for this inverter F antenna if so pls guide me

Note:
TAG: inverted F antenna----> measured readings
VSWR =1.4 @ 2.4GHz
S11 = -14 @ 2.4GHz
imp =36-j1.1
Please find the attached radiation pattern of the F antenna.

Thanks

I won't regard the reported behaviour as error rather than typical with the used antenna type. A circular polarized antenna would be needed to reduce the gain directional dependancy.

Inverted-F antenna derivates from Inverted-L antenna which is a bended monopole, so the antenna pattern in a particularly plane should be reasonable. Of course you have some deeps in the pattern but in the real life these will be compensated somehow by the environment.

Here are some IFA pattern examples:
http://focus.ti.com.cn/cn/lit/an/swru120b/swru120b.pdf

hi
FVm

I won't regard the reported behaviour as error rather than typical with the used antenna type. A circular polarized antenna would be needed to reduce the gain directional dependancy.

I know this F antenna is not unidirectional, but is there any way to minimize the gain variation

hi vFone

Inverted-F antenna derivates from Inverted-L antenna which is a bended monopole, so the antenna pattern in a particularly plane should be reasonable. Of course you have some deeps in the pattern but in the real life these will be compensated somehow by the environment

i am using Meandered Inverted F Antenna design

we are simulating in the real life environment condition, still we are getting gain variation in the antenna.... is there any way to minimize the gain variation of the antenn( by means tuning or matching or placement of the antenna placement )

The tuning of the antenna will not fix the antenna pattern, which is given mainly by the antenna type and shape. Finding the right place for the antenna, yes this can improve the antenna pattern.
But I don?t think that an RFID antenna should have a perfect circular pattern, when actually the TAG will be never placed in a free-space environment. In real life probably you get deeper multi-path variations than the deeps in your pattern.